Blokus (officially pronounced "Block us") is an abstract strategy game with transparent, Tetris-shaped, colored pieces that players are trying to play onto the board. The only caveat to placing a piece is that it may not lie adjacent to your other pieces, but instead must be placed touching at least one corner of your pieces already on the board.
There is a solitaire variation where one player tries to get rid of all the pieces in a single sitting.